I have to disagree. I work for Department of the Army, and our non-classified network (and certainly our classified network) will not allow the use of ANY external media. No CDs, thumb drives, or anything. Our computers still have USB ports, but even plugging your phone into one to charge it will set off alarms. Offices that routinely handle classified information do now allow any PEDs inside the office (Personal Electronic Devices). That includes cell phones, smart watches, etc.